Activate AT&T WiFI calling on a Tmobile S4?

Hello guys! Now that AT&T is supporting WiFi calling on a few android models, I was wondering if it was possible to activate the feature on T mobile phones being used in the AT&T network?
I have one Tmo S4 running on AT&T.

from xda-developers http://ift.tt/2dj9l6h
via IFTTT